Bending machine for metal rods

ABSTRACT

A bending machine for bending metal rods having a rotatable bending plate which carries a centrally disposed bending tool and at least one eccentric bending tool, means being provided for continuing angular movement of the rotatable bending plate beyond a nominal angular position in order to compensate for spring-back of a metal rod after a bend has been effected, there being impulse transmitting means actuable on rotation of the bending plate, means for counting impulses transmitted by said impulse transmitting means and means for comparing such transmitted impulses with a number of impulses pre-set in said counting means. The rotatable bending plate continues beyond the nominal bending angle by the provision of delay means which delay by a pre-selected variable period the moment at which the number of transmitted impulses corresponds to the number of impulses preset in the counting means. The period of said variable delay is proportional to the value of the nominal bending angle, the value of the ratio of the diameter of the centrally disposed bending tool to the diameter of the rod being bent and a factor, dependent upon the hardness of the rod, lying between 0.004 and 0.008.

United States Patent 1191 Peddinghaus 1 May 28, 1974 i 1 BENDlNG MACHINEFOR METAL RODS 22 Filed: Nov. 30, 1971 [21] Appl.No.:203,340

[30] Foreign Application Priority Data Nov. 30, 1970 Germany 2058793[52] US. Cl 72/21, .72/7, 72/D1G. 22, 72/702 [51] Int. Cl B2ld 7/024[58] Field of Search 72/7, 21, 8, 9, 10, ll,

72/12, DIG. 22, 702, 22.

[56] References Cited I UNITED STATES PATENTS 3,145,756 8/1964 Hill 72/73,156,287 11/1964 Munro 72/8 3,352,136 11/1967 Clarke 72/9 3,393,5437/l968 Van Gelder 72/26 3,407,850 10/1968 Kelm 72/702 3,459,018 8/1969Miller 72/7 3,512,383 5/1970 Arnold et al 72/22 3,661,002 5/1972Peddinghaus, Jr.. 72/21 3,670,541 6/1972 Peddinghaus 72/8 FOREIGNPATENTS OR APPLICATIONS 1,244,529 7/1967 Germany 72/149 PrimaryExaminerCharles W. Lanham Assistant Examiner-M. .l. Keenan Attorney,Agent, or Firm-Holman & Stern 57 ABSTRACT A bending machine for bendingmetal rods having a rotatable bending plate which carries a centrallydisposed bending tool and at least one eccentric bending tool, meansbeing provided for continuing angular movement of the rotatable bendingplate beyond a nominal angular position in order to compensate forspring-back of a metal rod after a bend has been effected, there beingimpulse transmitting means actuable on rotation of the bending plate,means for counting impulses transmitted by said impulse transmittingmeans and means for comparing such transmitted impulses with a number ofimpulses pre-set in said counting means. The rotatable bending platecontinues beyond th'e nominal bending angle by the provi-' sion of delaymeans which delay' by a pre-selected variable periodv the moment atrwhich the number of transmitted impulses correspondsto the number ofimpulses pre-set in the counting means. The period of said variabledelay is proportional to the value of the nominal bending angle, thevalue of the ratio of the diameter of the centrally disposed bendingtool to the diameter of the rod being bent and a factor, dependent uponthe. hardness of the rod, lying between 0.004 and 0.008.

' 6 Claims, 3 DrawingFigures PATENTEDIAY28 I914 3.812.694

SHEEI 1 (IF 2 4IVNV ENTOS BY A/ PATENTEDHAY 28 I974 SHEEI 2 0F 2 FIG. 3

BACKGROUND OF THE INVENTION The invention relates to a bending machinefor metal rods, such as steel reinforcing rods, the machine having abending plate which carries a central bending tool and at least oneeccentric bending tool, and being arranged to effect bends in bothangular directions, with the bending plate being automatically returnedto a starting position after it has turned through a required bendingangle.

PRIOR TECHNIQUES In bending machines of this type, a bent rod willspring back elastically a limited amount after a bend has been made.Since, after a bend which was set at a specific nominal bending anglehas been made, the angle of thebend would be too'small because of thisspring-back. certain adjustments must be made, using test bends, untilthe required bend is achieved. It is.

known that cams for instance can be used to make such adjustments, withthese cams beinginserted in various holes on the periphery of a discwhich rotates with the bending plate. It has also been suggested thatthe bending operation can be set to continue automatically after apreselected bending angle has been achieved, so that the spring-backalready mentioned is compensated for. It has further been suggested thata standing value indicator can be used, by means of which the driveremains switched on, after a predetermined-bending angle has beenachieved, for a further time which is the same as the idlingtime,-namelythe time taken by the bending plate initially until its bending toolsare loaded and the initial resilience of the rod to be bent has beentaken up. Here too, however, a test bend must first of all be made andmeasured in order for the standing value indicator to be set, saidindicator comprising, for example, a potentiometer which can vary thetimeconstants of an RC network.

OBJECTS AND SUMMARY OF THE INVENTION In distinction to the aboveexpedients, the object of this invention is to provide an improvedbending machine of the type described in the introduction so'that suchtest bends or measuring operations are not needed except for a singletest bar bend. I

In accordance with the invention, there is provided a bending machinefor bending metal rods having a rotatable bending platewhich carries acentrally disposed bending tool and at least one eccentric bending tool,a series of electrical contact means rotatable with said bending plateand angularly spaced at positions corresponding to the nominal value ofvarious required bends, impulse transmitting means actuable by saidcontact means on rotationthereof, a counter for recording impulsesreceived from said impulse transmitting means and means for pre-settingin said counter a pre-determined number of impulses corresponding to anygiven required bending angleand means for reversing the angularmovement'of said bending'platesoas to return it to a zero position at amoment when the number of impulses transmitted by said impulsetransmitting means corresponds to the number of impulses pre-set in saidcounter, characterized in that, for any given nominal bending angle,means are provided for delaying, by a preselected variable period, themoment at which the number of impulses transmitted by said impulsetransmitting means corresponds to the number of impulses pre-set in saidcounter, thereby permitting the bending plate to rotate through an anglegreater than said nominal bending angle, the period of said delay beingproportional to the value of the nominal bending angle, the value of theratio of the diameter of the centrally disposed bending tool to thediameter of the rod being bent and a factor, dependent upon the hardnessof said rod, lying between 0.004 and 0.008.

With an average strength of reinforcing steel rods a constantproportionality factor of about 0.0063 can be used.

It is therefore particularly possible, in accordance with the invention,to do away with test bends or measuring operations during the bendingprocess. In practice the value of the ratio bending tool diameter/roddiameter only has to be adjusted if one changes over to other diameters.Thetool which is fitted centrally on the bending plate is considered tobe the bending tool in the sense of the invention. Since this tool inparticular is frequently left unchanged, only the diameter of the rodneeds to be considered, in most cases, in order to compensate for thespring-back resilience in the manner described in the invention. Sincesaid rod diameter is always known this simplifies considerably the wayin which the machine works.

The electrical contact means are arranged for convenience on adisc whichrotates with the bending plate, saidcontact means actuating an impulsetransmitter of which the impulses are recorded .by a switch meter orcounter which can be adjusted by an adjusting switch on which thebending angles are marked, to a number of impulses corresponding to thepre-selectedbending angle. Said contact means may comprise a' singlecontact at each of a plurality of positions corresponding to therequired nominal bending angles and in this case the contacts'may beadjusted by a common adjusting device, on which then only the ratio ofthe bending tool diameter/rod diameter has still to-be adjusted. Due

to the adjustment of this ratio all contacts on the disc then alter byan amount which increases proportionally as the nominal bending angleincreases.-ln another embodiment it is advantageous to have severalcontacts at I each of the nominal bending angle positions and in thiscase the number of impulses which are to be pre-set in the counter canbe varied as required so that for any given nominal bending angle avariable number of said contacts has to actuate the impulse transmittingmeans before parity is achieved with the aforesaid pre-set number ofimpulses. v

In addition a further method which can be used is for the electricalcontact means to be delayed electrically, for instance by means of RCnetworks.

BRIEF DESCRIPTION OF THE DRAWINGS The invention .will now be moreparticularly de-.

FIG. 2 is a fragmentary plan view showing means whereby the position ofan electrical contact on the ad justingdisc can be varied, and

FIG. 3 is a schematic view showing an alternative form of adjusting discand means, associated with said disc, for setting various bendingangles.

DETAILED DESCRIPTION OF THE I EMBODIMENTS Referring to FIG. 1, thebending machine shown therein has a bending plate 1 which carries acentral bending tool 2 and an eccentric bending tool 3. Between saidbending tools, a rod 4 which is to be bent is placed, said rod beingsupported in a known way is driven with the bending plate by anysuitable andconventional drive means (not shown) such as an electricmotor, with said disc 9 supporting in addition to a zero contact 10 atleast th'reefurther contacts (not shown) atpositions ll, "12 and 13corresponding to bending angles 45, 90 and 180.The contacts are arrangedto actuate animpulse transmitting means including contacts indicated byreference numeral 14 the impulses from whichare counted-in a mannerwhich is not the subject of the present invention, whereby after aspecific number'of impulses, the aforesaid motor or drive means will bestopped and reversed to return the bending plate to its initialposition.

In FIG. 1, the contacts 11 and 12 are shown on the righthand side of thedisc 9 as seen in the drawing. It will be appreciated, however, that inpractice similar contacts will be provided on the left-hand side of thedisc 9 since, of course, it may be required to drive the bending plate1,-togetherwith the disc 9, in a clockwise direction as well as ananti-clockwise direction depending on what kind of bend is required. Allsuchcontacts are arranged, however, so that on passing the contacts14(whichare connected in an impulse transmitting circuit) an impulsewill be transmitted to a counter (not shown) which can be of any knownform.

Also, in accordance "with known practice, a preselected number ofimpulse's'can be set in such 'a counter so that the'number of suchpre-set impulses is compared with the number of impulses received fromthe impulse transmitting circuit of which the contacts 14 form apart.When these two numbers of impulses are equal-then the aforesaid counteris arranged so that a signal is'applied to the drive motor of thebending plate to cause'such drive motor to be reversed in order toreturn the bending plate to its initial position.

FIG. 2 shows a part of an adjusting disc 9 in which two successivecontacts indicated by reference numer als I5 and 16 can be seen. Thesecontactors can slide along arcuate slits l7 and 18, for which purpose aforked end 19 of a lever ZO-engageseach contact, with said fork beingslit in a radial direction. Each lever 20 has a fulcrum 21 which isconnected to the adjusting disc 9, whereby the positions of the fulcrumpoints 21,

22 in successive levers is-such that they are disposed at increasingradial distances fromthe associated slits 17, 18 in proportion to theirangular distance from each. other. A further but smaller. disc 23 ismounted concen-. trically onthe adjusting disc 9, with said disc 23being constructed with slotted brackets or slits 24 and 25, into whichthe inner ends of 'said levers project. In addition, the disc 23 isprovided with a scale 26 which can be set against a mark 27 on the disc9, the scale being marked with a plurality of various values for theratio of bending tool diameter to rod diameter, i.e., the distance 7divided by the distance 8. Thus, if the disc 23 is moved in thedirection of the arrow 28 the contactors l5, 16 will be moved by saidleversso that there is a proportional increase, in the forward direction29 of movement of the adjusting disc 9, in the distances by which saidcontactors are advanced in their arcuate slits 17 and 18.

With the apparatus shown in FIG. 2 it will be appreciated that the onlyadjustment which will normally be required is that involving angularmovement of the disc 23 in order to compensate, if necessary, for avariation in the value of the ratio of the bending tool diameter to therod diameter, it being understood that the different positions of thefulcrum points 21, 22 will also compensate for the different nominalbending angles. The apparatus is, however, designed so that theadjustment made by the disc'23. will also include a further factor,

namely a factor which is dependent upon the hardness of the rod beingbent and which lies within the range of 0.004 and 0.008, a preferredvalue of such factor being 0.0063. l

It was determined that the actual bending angle which has to be imparteddepends firstly on the nominal value or the required final value of thebending an-.

. pirical and is very easily determined by experiment for any particulargrade of steel. One can take a test bar and bend it experimentally so asto finish up with acertain nominal bending angle, the total anglethrough which the bar is bent being greater, of course, than the nominalor final value by the amount of the spring-back angle. The spring-backangle can thus be measured experimentally in this one test bend and ifthis angle is then divided by the product of the nominal value of thebending angle and the ratio of the diameters of the bending tool and thebar, the above-stated factor will be determined for that particulargrade of steel. It is pointed out that the above-mentioned factor ispurely empirical, can easily be determined by one experimental bend, andis a constantfor any particular grade of steel.

Ordinarily, the hardness of rods being bent bythe bending machine willnot alter significantly. If, however, the hardness does vary to anextent which makes it necessary to vary the above-mentioned factorwithin the range stated, then the radial positions of said fulcrumpoints are altered and this can be effected by arranging that saidfulcrum points 21 and 22 are themselves mounted in radially extendingslits so that their radial positions on the disc 9 can be varied.

. In an alternative embodiment shown in FIG. 3 an adjusting disc 9 showntherein has further contacts 15',

16' closely adjacent to contactors 15, 16 respectively. Thus, at each ofa plurality of positions corresponding respectively to the nominalbending angles, there is a group of contacts such as and 15' or 16 and16. An impulse transmitting means having contacts similar to thecontacts indicated diagrammatically by reference 14 in FIG. 1, is alsoactuated by these contacts 15 and 15 or 16 and 16'. The impulses fromsaid transmitting means are then supplied to an impulse counter 30 whichis set to a specific pre-determined number of impulses by means of anadjusting switch 31, and which then controls the electric motor'drivingthe bending plate through an electric conduit 32 connected thereto. Forsetting the adjusting switch 31, there is provided an adjusting disc 33which has various angle markings 34. A shaft 35 and a shaft 36 aredisposed between the adjusting disc 33 and the adjusting switch 31 andare connected together by a gear 37 which is infinitely variable in therange of l l to l L1. This gear can, for instance, as shown be made upof two frusto-conical parts 38 and 39 which are connected together by abelt 40 which can be moved in an axial direction. An adjusting fork 41is provided for adjusting the position of the belt 40, with said forkhaving a part movable in a slot 42. There is also an indicator 43 whichpoints to a scale 44 on which the various values of the ratio of tooldiameter/rod diameter (seven-eighths) as before can be adjusted. In thisway a specific bending angle can be set by adjusting disc 33. However,as a result of the aforesaid gear 37 and adjusting switch 31,-a greaternumber of impulses will be set on the switch meter 30 than correspondsto the nominal angle of rotation of the bending plate. In order to stopand reverse the drive of the bending plate several additional impulsetransmissions must be given and these are triggered off by thecontactors 15 or 16' so that in this way the spring-back angles can becompensated for.

With the embodiment shown in FIG. 3, it is thus possible to vary thenumber of impulses pre-set in the counter 30 by means which compensateboth for the nominal bending angle and also for the value of the ratioof the bending tool diameter to the rod diameter. As above-described thelast-mentioned ratio is varied by sliding the fork 41 to the right orleft without rotation, the position of the fork being fixed by means ofsome suitable clamp operating in the slot 42. a

The above-mentioned ratios by which the gear 37 can be varied, namelyavariation within the range of l l to l 1.1, will, it will beappreciated, provide for a variation of up to 10 percent so that, forexample, when a nominal bending angle of 90 is required, an additionalbending angle to compensate for the spring-back effect of up to 9 can beset and in practice such an addition is found to be more thansufficient.

As is the case with the embodiment shown in FIG. 2, the aforementionedfactor, dependent upon the hardness of the rod being bent, will normallyremain constant at the preferred value of 0.0063. If, however, it isrequired to vary this factor because of varying hardness of the rodbeing bent, then suitable compensation can be effected by moving the twoparts 38 and 39 of the gear 37 axially relative to each other, withmeans being provided to ensure that the tension of the belt 40 iscorrectly adjusted. As an alternative to this, the aforementionedfactor, dependent upon the hardness of the rod, can also be adjusted byarranging so that the fork 41 is, in addition to being movable to rightor left along the 6 slot 42, is also pivotable, for example, aboutapivot which connects said fork 41 to a slide which moves in said slot42. In this case, a dial can be mounted on such pivot and on this dialwould be marked various values tor can easily be set. In any event, itwill be appreciated that with the embodiment shown in FIG. 3, the numberof impulses pre-set in the counter 30 can be varied in order to delaythe moment when impulses received by operation of the contacts 15, 15',16 and 16 equal the number of pre-set impulses in order that the bendingplate drive motor can be reversed. On the other hand, with theembodiment shown in FIG. 2, the number of pre-set impulses will remainthe same but the appropriate delay to compensate for spring-back isachieved by altering the positions of the contacts themselves on thedisc 9.

1 claim:

1. A bending machine for bending metal rods having a rotatable bendingplate which carries a centrally disposed bending'tool and at least oneeccentric tool,'a-series of electrical contact means rotatable with saidbending plate and angularly spaced atpositions corresponding to thenominal value of various required bends, impulse transmitting meansactuable by said contact means on rotation thereof, a counterfor-recording impulses received from said impulse transmitting means andmeans for pre-setting, in said counter, a pre-determined number ofimpulses corresponding to any given required bending angleand means forreversing the angular movement of said bending plate so as to return itto a zero position at a moment when the number of impulses transmittedby said impulse transmitting means corresponds to the number of impulsespre-set in said counter, characterized in that, for any given nominalbending angle, means are provided for delaying, by a preselectedvariable period, the moment at which the number of impulses transmittedby said impulse transmitting means corresponds to the number of impulsespre-set in said counter, thereby permitting the bending plate to rotatethrough an angle greater than said nominal bending angle, the period ofsaid delay being proportional .to the value of the nominal bendingangle, and the value of the ratio of the diameter of the centrallydisposed bending tool to the diameter of the rod being bent.

2. The bending machine as claimed in claim 1 wherein said electricalcontact means comprises a single contact at each of a plurality ofangularly spaced positions corresponding to said nominal bending angles,the contacts being mounted on a disc rotatable with the bending plateand wherein said delaying means comprises means for angularly retardingsaid contacts on said disc.

3. The bending machine as claimed in claim 2 wherein each contact ismounted for movement in an arcuate slot formed in said disc and isengageable by one end of a radially extending lever pivotally connectedintermediate its ends on said disc, the other ends of said levers beingengageable by a rotatable adjusting member and the pivots of said leversbeing disposed at varying distances from the ends thereof engageablewith said contacts whereby rotation of said adjusting member willsimultaneously pivot said levers so that the contacts will be moved intheir arcuate slots sponding' to a plurality of nominal bending anglesand wherein said delaying means comprises means for increasing, by apre-selected, variable amount, the num ber of impulses pre-set in saidcounter'for any required bending angle.

6. The bending machine as claimed in claim 5 wherein said means forincreasing the number of impulses pre-set in said counter comprises arotatable setting member and an adjusting switch which areinterconnected by means of a variable-ratio gear. Y

1. A bending machine for bending metal rods having a rotatable bendingplate which carries a centrally disposed bending tool and at least oneeccentric tool, a series of electrical contact means rotatable with saidbending plate and angularly spaced at positions corresponding to thenominal value of various required bends, impulse transmitting meansactuable by said contact means on rotation thereof, a counter forrecording impulses received from said impulse transmitting means andmeans for pre-setting, in said counter, a pre-determined number ofimpulses corresponding to any given required bending angle and means forreversing the angular movement of said bending plate so as to return itto a zero position at a moment when the number of impulses transmittedby said impulse transmitting means corresponds to the number of impulsespre-set in said counter, characterized in that, for any given nominalbending angle, means are provided for delaying, by a pre-selectedvariable period, the moment at which the number of impulses transmittedby said impulse transmitting means corresponds to the number of impulsespre-set in said counter, thereby permitting the bending plate to rotatethrough an angle greater than said nominal bending angle, the period ofsaid delay being proportional to the value of the nominal bending angle,and the value of the ratio of the diameter of the centrally disposedbending tool to the diameter of the rod being bent.
 2. The bendingmachine as claimed in claim 1 wherein said electrical contact meanscomprises a single contact at each of a plurality of angularly spacedpositions corresponding to said nominal bending angles, the contactsbeing mounted on a disc rotatable with the bending plate and whereinsaid delaying means comprises means for angularly retarding saidcontacts on said disc.
 3. The bending machine as claimed in claim 2wherein each contact is mounted for movement in an arcuate slot formedin said disc and is engageable by one end of a radially extending leverpivotally connected intermediate its ends on said disc, the other endsof said levers being engageable by a rotatable adjusting member and thepivots of said levers being disposed at varying distances from the endsthereof engageable with said contacts whereby rotation of said adjustingmember will simultaneously pivot said levers so that the contacts willbe moved in their arcuate slots by different angular displacementsdependent upon the positions of said lever pivots.
 4. The bendingmachine as claimed in claim 3 wherein means are provided for adjustingthe radial positions of the pivots of said levers.
 5. The bendingmachine as claimed in claim 1 wherein a plurality of closely adjacentcontacts are provided at each of a plurality of angular positionscorresponding to a plurality of nominal bending angles and wherein saiddelaying means comprises means for increasing, by a pre-selected,variable amount, the number of impulses pre-set in said counter for anyrequired bending angle.
 6. The bending machine as claimed in claim 5wherein said means for increasing the number of impulses pre-set in saidcounter comprises a rotatable setting member and an adjusting switchwhich are interconnected by means of a variable-ratio gear.